135822-93-4Relevant academic research and scientific papers
A [3 + 2] and [4 + 3] cycloaddition approach to N-heterocycles via Pd-catalyzed TMM reactions with imines
Trost, Barry M.,Marrs, Christopher M.
, p. 6636 - 6645 (2007/10/02)
The question of cycloadditions of (trimethylenemethane) palladium complexes to heteroation is probed in the context of pyrrolidine syntheses. Whereas simple imines fail to react, imines possessing an electron-withdrawing group at either the carbon or nitrogen enhance the electrophilicity of the imine sufficiently to make it an excellent accetor. Palladium(0) complexes catalyze cycloadditions of 2-((trimethylsilyl)methyl)allyl esters to N-tosyl- and N-nitroimines. The stronger electron-withdrawing nature of the nitre group permits nitrimines derived from relatively hindered ketones to participate. Conjugated cisoid imines lead to [4 + 3] cycloadditions - a process azepine synthesis. Substituted TMM precursors cycloadd with high regioselectivity. The result. are consistent with a two-step addition process. Some of the simple examples explored to determine the scope and limitations of the process reveal simple syntheses of proline and nicotine analogues. The successful employment of imines as direct acceptors for TMM-PdL2 opens a new chapter on metal-catalyzed cycloadditions.
